This invention relates to a stator assembly for an axial flow rotary machine and more particularly to structure for actuating a device for selectively flowing air from a working medium flowpath of the machine. While the invention was conceived in the field of axial flow, gas turbine engines for bleeding air at a point between two compressor rotor assemblies, it has application to other devices in such engines that employ an actuating ring.
Axial flow gas turbine engines include a compression section, a combustion section and a turbine section. A flowpath for medium gases extends through these sections of the engine. During operation, the gases are pressurized in the compression section and fuel is added in the combustion section. The fuel is burned to add energy to the pressurized gases. The hot, pressurized gases are expanded through the turbine section to provide the work of compression and hot, high pressure gases for subsequent use.
U.S. Pat. No. 4,827,713 issued to Paterson et al entitled xe2x80x9cStator Valve Assembly for a Rotary Machinexe2x80x9d is an example of such a gas turbine engine. In Paterson, the compression section of the engine is provided with two independent mechanical compressors. During transient operating conditions, one compressor can provide more flow than can be accommodated by the second compressor. Accordingly, the compression section is provided with a plurality of passages extending about the working medium flowpath to allow a portion of the air to escape from the compression section. In particular, the engine has a housing extending circumferentially about the axis of the engine. The housing has a plurality of openings. Each opening is covered or uncovered by an axially translating valve ring having circumferentially extending seal surfaces which move axially to engage resilient seal members. The valve ring is moved from an opened to a closed position by actuating means and includes guide roller assemblies in one ring and guide slots in the other ring.
The engine has circumferentially extending resilient seal members which extend axially. In the closed position, the seal members extend between a valve ring and the seal surface. The valve ring is urged by simple actuating means from an open position to a closed position to axially compress the resilient seal members on either side of the openings to provide a gas tight seal.
The valve ring is movable between an opened and a closed position and being guided by a slot and guide pin combination for urging the valve ring axially against resilient sealing members, the slots being contoured to provide a mechanical advantage as the axial compressive force is applied to the resilient sealing members.
The valve ring is movable between an open position and a closed position. The ring is guided by a slot and pin (cam follower) configuration, the slot having a preselected contour as the ring compresses the resilient seal members such that an inclined plane effect is provided during compression. In one embodiment, a feature is a bushing which engages the cam follower and the adjacent stator structure as the valve ring is moved to the open position.
As will be realized, the loss of working medium gases through the openings under steady state conditions when the compressors are operating at their design point will cause a decrease in the efficiency of the engine. Accordingly, it is desirable to insure that flow does not occur through these openings under conditions which do not require the diversion of flow from the flowpath.
Another problem is wear on the surface of the track opening and fracture failures of the pin which holds the hardface roller assembly in engagement with the track opening. A particular concern of the prior art design shown in FIG. 10 is the potential failure of the roller assembly occasioned by the shank breaking or by the thrust element at the head of the pin coming free and allowing the rotatable element of the roller to fall into the engine and degrade the performance of the engine. For example, the roller assembly has a thrust element which is bonded or mechanically attached to the pin. Experience has shown that this thrust element has the capability to become separated from the pin.
The above art notwithstanding, scientists and engineers working under the direction of Applicant""s assignee have sought to decrease leakage through such seals by improving the sealing effectiveness of the seals and decreasing the effect that distortion resulting from operative load has on seal components.
According to the present invention, a method for forming a track for guiding a roller assembly in a rotary machine includes forming a liner having walls for guiding the roller assembly along the track and disposing the liner in a stator assembly in the rotary machine.
In accordance with one embodiment, the method includes forming an opening for the liner in the assembly and disposing the liner in the opening at a predetermined location and forming the liner of a different, harder material than the stator assembly while accommodating differences in thermal growth between the liner and the rotary machine.
In accordance with one detailed embodiment, the method includes enlarging a preexisting opening in the assembly having worn walls which bound the track, and disposing a liner in the assembly having walls contoured to provide substantially the same path as the walls of the preexisting opening originally provided.
In accordance with another detailed embodiment, the method includes removing an existing liner from the assembly and replacing the liner with a new liner having a modified contour to modify the track followed by the roller assembly.
A primary feature of the present method is the step of disposing a liner in a rotary machine to form a track for the roller assembly. Another feature is forming a contour in the liner. Still another feature, in one embodiment, is the step of removing a preexisting liner which enables modifying or repairing the track for the roller assembly without replacing major components.
A primary advantage of the present invention is the cost and ease of forming and maintaining a rotary machine which results from the ability to replace a small precisely formed liner which forms the track for a roller assembly instead of the entire massive stator assembly which is used to support the liner. Another advantage is the ease of developing new gas turbine engines or modifying current gas turbine engines by using the same assembly for supporting the liner and modifying the path of the roller assembly by modifying the shape of the liner rather than forming a new assembly for guiding the roller assembly. Still another advantage is the manufacturing ease and durability which results from forming the stator assembly, such as a housing, from an easily machined lightweight material and forming a liner from a harder and heavier material.